To generate mixed light, that is to say non-monochromatic light and in this case, for example, white light, it is customarily possible, when light-emitting diodes (LEDs) are used, to employ LEDs that emit in different colors and/or a plurality of luminescent materials. To generate white light, for example, spectral components in the yellow-green and the red wavelength ranges which are radiated by different LEDs can be superimposed.
What is challenging, in addition to meeting optical requirements, such as, for example, the mixing of light emitted by different LED chips, is also the stabilization of the color location, for example, of the white point in the case of white light, with respect to temperature. This relates, for example, to different temperature dependencies of the chip technologies involved. A stabilizing element is shown in the non-prior-published DE 10 2008 057 347.7.
Also of interest, in addition to the stabilization of the color location, is the possibility of controlling the color temperature (CCT) of such a light source, for example, to vary between warm-white light and cold-white light. Typical implementations of color-temperature-controllable light sources have an optical and/or thermal sensor, a microcontroller and a plurality of LED drivers to control the LEDs. For the compensation of thermal effects, typical LED characteristics are stored in the microcontroller.
The problem posed is that of defining a color-temperature-controllable and color-location-stabilized light source of simple construction.